[PATCH] Ensure captured_main has unique address

[PATCH] Ensure captured_main has unique address

[Tom de Vries]

Hi,

atm selftest.exp fails for me.

One of the reasons is that after setting a breakpoint in captured_main, we
stop at:
...
Breakpoint 1, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
...
while selftest_setup expects to stop at captured_main.

The problem is that captured_main_1 has been inlined into captured_main, and
captured_main has been inlined into gdb_main:
...
$ nm ./build/gdb/gdb | egrep ' [tT] .*captured_main|gdb_main' | c++filt
000000000061b950 T gdb_main(captured_main_args*)
...

The reason that we seem to be stopping at inline function captured_main_1 has
probably something to do with commit "Don't elide all inlined frames", which
shows us the frames of inlined functions as if they were not inlined.  Indeed,
the two inlined functions show up in the backtrace:
...
(gdb) bt
#0  captured_main_1 (context=<optimized out>) at main.c:492
#1  captured_main (data=<optimized out>) at main.c:1147
#2  gdb_main (args=args@entry=0x7fffffffdb80) at main.c:1173
#3  0x000000000040fea5 in main (argc=<optimized out>, argv=<optimized out>)
    at gdb.c:32
...

[ For contrast, If I use my distro gdb to debug build/gdb/gdb instead, we just
get:
...
Breakpoint 1, gdb_main (args=args@entry=0x7fffffffdb80)
    at src/gdb/main.c:1173
1173          captured_main (args);
...
]

Either way, this patch fixes the problem by ensuring that captured_main has a
unique address:
...
$ nm ./build/gdb/gdb | egrep ' [tT] .*captured_main|gdb_main' | c++filt
000000000061ca20 T gdb_main(captured_main_args*)
000000000061c980 t captured_main(void*)
000000000061b950 t captured_main_1(captured_main_args*)
...

Tested selftest.exp (with two other selftest.exp related fixes applied).

OK for trunk?

Thanks,
- Tom

[gdb] Ensure captured_main has unique address

2018-06-12  Tom de Vries  <tdevries@suse.de>

	* main.c (captured_main, captured_main_1): Add
	__attribute__((noinline)).

---
 gdb/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gdb/main.c b/gdb/main.c
index 9694af2426..f35dffd428 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -447,7 +447,7 @@ struct cmdarg
   char *string;
 };
 
-static void
+static void __attribute__((noinline))
 captured_main_1 (struct captured_main_args *context)
 {
   int argc = context->argc;
@@ -1139,7 +1139,7 @@ captured_main_1 (struct captured_main_args *context)
     }
 }
 
-static void
+static void __attribute__((noinline))
 captured_main (void *data)
 {
   struct captured_main_args *context = (struct captured_main_args *) data;

Change inline frame breakpoint skipping logic (Re: [PATCH] Ensure captured_main has unique address)

[Pedro Alves]

On 06/12/2018 04:06 PM, Tom de Vries wrote:
> Hi,
> 
> atm selftest.exp fails for me.
> 
> One of the reasons is that after setting a breakpoint in captured_main, we
> stop at:
> ...
> Breakpoint 1, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
> ...
> while selftest_setup expects to stop at captured_main.
> 
> The problem is that captured_main_1 has been inlined into captured_main, and
> captured_main has been inlined into gdb_main:
> ...
> $ nm ./build/gdb/gdb | egrep ' [tT] .*captured_main|gdb_main' | c++filt
> 000000000061b950 T gdb_main(captured_main_args*)
> ...
> 
> The reason that we seem to be stopping at inline function captured_main_1 has
> probably something to do with commit "Don't elide all inlined frames", 

Yes, sounds like it.  But the selftest.exp explicitly asks to stop
at "captured_main", not "captured_main_1", so I'm thinking that
it's gdb's behavior that might be wrong:

 (top-gdb) b captured_main
 Breakpoint 3 at 0x792f99: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb 
 
 Breakpoint 3, captured_main_1 (context=<optimized out>) at /home/pedro/gdb/binutils-gdb/src/gdb/main.c:492
 492       lim_at_start = (char *) sbrk (0);
 (top-gdb) 

With the patch below, we instead get:

 (top-gdb) b captured_main
 Breakpoint 6 at 0x791339: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb 

 Breakpoint 6, captured_main (data=<optimized out>) at src/gdb/main.c:1147
 1147      captured_main_1 (context);
 (top-gdb) 

and:

 (top-gdb) b captured_main_1
 Breakpoint 7 at 0x791339: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb 
 Breakpoint 7, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
 492       lim_at_start = (char *) sbrk (0);
 (top-gdb) 

Note that both captured_main and captured_main_1 resolved to the
same address, 0x791339.  The gdb.base/inline-break.exp testcase
currently does not exercise that, but the new test added by the
patch below does.  That new test fails without the patch and passes
with the patch.  No regressions on x86-64 GNU/Linux.  WDYT?

Also, while looking at stopped_by_user_bp_inline_frame I noticed
that comparing the THIS_PC is basically a nop -- if a software or
hardware breakpoint explains the stop, then it must be that it
was installed at the current PC.

From cf6924a2cfca397b80c7c935e048771de77d3105 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Tue, 12 Jun 2018 18:22:25 +0100
Subject: [PATCH] Inline breakpoints

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* inline-frame.c (stopped_by_user_bp_inline_frame): Replace PC
	parameter with a block parameter.  Compare location's block symbol
	with the frame's block instead of addresses.
	(skip_inline_frames): Pass the current block instead of the
	frame's address.  Break out as soon as we determine the frame
	should not be skipped.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* gdb.opt/inline-break.c (func_callee, func_caller): New.
	(main): Call func_caller.
---
 gdb/inline-frame.c                     | 23 +++++++++++------------
 gdb/testsuite/gdb.opt/inline-break.c   | 21 +++++++++++++++++++++
 gdb/testsuite/gdb.opt/inline-break.exp | 17 +++++++++++++++++
 3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index 1ac5835438d..3edd5b2b20b 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -286,11 +286,10 @@ block_starting_point_at (CORE_ADDR pc, const struct block *block)
 }
 
 /* Loop over the stop chain and determine if execution stopped in an
-   inlined frame because of a user breakpoint.  THIS_PC is the current
-   frame's PC.  */
+   inlined frame because of a user breakpoint set at FRAME_BLOCK.  */
 
 static bool
-stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
+stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 {
   for (bpstat s = stop_chain; s != NULL; s = s->next)
     {
@@ -301,9 +300,9 @@ stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
 	  bp_location *loc = s->bp_location_at;
 	  enum bp_loc_type t = loc->loc_type;
 
-	  if (loc->address == this_pc
-	      && (t == bp_loc_software_breakpoint
-		  || t == bp_loc_hardware_breakpoint))
+	  if ((t == bp_loc_software_breakpoint
+	       || t == bp_loc_hardware_breakpoint)
+	      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 	    return true;
 	}
     }
@@ -340,12 +339,12 @@ skip_inline_frames (ptid_t ptid, bpstat stop_chain)
 		{
 		  /* Do not skip the inlined frame if execution
 		     stopped in an inlined frame because of a user
-		     breakpoint.  */
-		  if (!stopped_by_user_bp_inline_frame (this_pc, stop_chain))
-		    {
-		      skip_count++;
-		      last_sym = BLOCK_FUNCTION (cur_block);
-		    }
+		     breakpoint for this inline function.  */
+		  if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
+		    break;
+
+		  skip_count++;
+		  last_sym = BLOCK_FUNCTION (cur_block);
 		}
 	      else
 		break;
diff --git a/gdb/testsuite/gdb.opt/inline-break.c b/gdb/testsuite/gdb.opt/inline-break.c
index 922102debb6..6ad331fcc63 100644
--- a/gdb/testsuite/gdb.opt/inline-break.c
+++ b/gdb/testsuite/gdb.opt/inline-break.c
@@ -176,6 +176,25 @@ not_inline_func3 (int x)
   return y + inline_func3 (x);
 }
 
+/* A static inlined function that is called by another static inlined
+   function.  */
+
+static inline ATTR int
+func_callee (int x)
+{
+  return x * 23;
+}
+
+/* A static inlined function that calls another static inlined
+   function.  The body of the function is a simple as possible so that
+   both functions are inlined to the same PC address.  */
+
+static int
+func_caller (int x)
+{
+  return func_callee (x);
+}
+
 /* Entry point.  */
 
 int
@@ -205,5 +224,7 @@ main (int argc, char *argv[])
 
   x = not_inline_func3 (-21);
 
+  func_caller (1);
+
   return x;
 }
diff --git a/gdb/testsuite/gdb.opt/inline-break.exp b/gdb/testsuite/gdb.opt/inline-break.exp
index 008ff1ac33a..f1ab3d23715 100644
--- a/gdb/testsuite/gdb.opt/inline-break.exp
+++ b/gdb/testsuite/gdb.opt/inline-break.exp
@@ -231,4 +231,21 @@ foreach_with_prefix cmd [list "break" "tbreak"] {
     }
 }
 
+# func_caller and func_callee are both inline functions, and one calls
+# the other.  Test that setting a breakpoint on the caller reports the
+# stop at the caller, and that setting a breakpoint at the callee
+# reports a stop at the callee.
+foreach_with_prefix func {"func_callee" "func_caller"} {
+    clean_restart $binfile
+
+    if {![runto main]} {
+	untested "could not run to main"
+	continue
+    }
+
+    gdb_breakpoint $func
+    gdb_test "continue" "Breakpoint .* $func .*at .*$srcfile.*" \
+	"continue to inline function"
+}
+
 unset -nocomplain results
-- 
2.14.3

Re: Change inline frame breakpoint skipping logic (Re: [PATCH] Ensure captured_main has unique address)

[Tom de Vries]

On 06/12/2018 07:38 PM, Pedro Alves wrote:
> On 06/12/2018 04:06 PM, Tom de Vries wrote:
>> Hi,
>>
>> atm selftest.exp fails for me.
>>
>> One of the reasons is that after setting a breakpoint in captured_main, we
>> stop at:
>> ...
>> Breakpoint 1, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
>> ...
>> while selftest_setup expects to stop at captured_main.
>>
>> The problem is that captured_main_1 has been inlined into captured_main, and
>> captured_main has been inlined into gdb_main:
>> ...
>> $ nm ./build/gdb/gdb | egrep ' [tT] .*captured_main|gdb_main' | c++filt
>> 000000000061b950 T gdb_main(captured_main_args*)
>> ...
>>
>> The reason that we seem to be stopping at inline function captured_main_1 has
>> probably something to do with commit "Don't elide all inlined frames", 
> 
> Yes, sounds like it.  But the selftest.exp explicitly asks to stop
> at "captured_main", not "captured_main_1", so I'm thinking that
> it's gdb's behavior that might be wrong:
> 
>  (top-gdb) b captured_main
>  Breakpoint 3 at 0x792f99: file src/gdb/main.c, line 492.
>  (top-gdb) r
>  Starting program: build/gdb/gdb 
>  
>  Breakpoint 3, captured_main_1 (context=<optimized out>) at /home/pedro/gdb/binutils-gdb/src/gdb/main.c:492
>  492       lim_at_start = (char *) sbrk (0);
>  (top-gdb) 
> 
> With the patch below, we instead get:
> 
>  (top-gdb) b captured_main
>  Breakpoint 6 at 0x791339: file src/gdb/main.c, line 492.
>  (top-gdb) r
>  Starting program: build/gdb/gdb 
> 
>  Breakpoint 6, captured_main (data=<optimized out>) at src/gdb/main.c:1147
>  1147      captured_main_1 (context);
>  (top-gdb) 
> 
> and:
> 
>  (top-gdb) b captured_main_1
>  Breakpoint 7 at 0x791339: file src/gdb/main.c, line 492.
>  (top-gdb) r
>  Starting program: build/gdb/gdb 
>  Breakpoint 7, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
>  492       lim_at_start = (char *) sbrk (0);
>  (top-gdb) 
> 

Agreed, that's a better solution.

> Note that both captured_main and captured_main_1 resolved to the
> same address, 0x791339.  

Right. I played around a bit with this, and set breakpoints on
captured_main and captured_main_1.

If I set a breakpoint on captured_main_1, we have captured_main unknown:
...
Breakpoint 2, captured_main_1 (context=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:492
492       lim_at_start = (char *) sbrk (0);
(gdb) p captured_main
No symbol "captured_main" in current context.
(gdb) p captured_main_1
$1 = {void (captured_main_args *)} 0x61b959
<gdb_main(captured_main_args*)+25>
...

But If I set a breakpoint on captured_main instead, we have
captured_main_1 unknown:
...
Breakpoint 3, captured_main (data=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:1147
1147      captured_main_1 (context);
(gdb) p captured_main
$2 = {void (void *)} 0x61b959 <gdb_main(captured_main_args*)+25>
(gdb) p captured_main_1
No symbol "captured_main_1" in current context.
...

And if I set a breakpoint on both, captured_main_1 seems to take
precedence (independent of the order used to set the breakpoint):
...
Breakpoint 1, captured_main_1 (context=<optimized out>)
    at /home/vries/gdb_versions/devel/src/gdb/main.c:492
492       lim_at_start = (char *) sbrk (0);
(gdb) p captured_main_1
$1 = {void (captured_main_args *)} 0x61b959
<gdb_main(captured_main_args*)+25>
(gdb) p captured_main
No symbol "captured_main" in current context.
...

I don't understand the underlying mechanisms well enough to decide
whether this is a problem or not, but I thought I just mention it.

> The gdb.base/inline-break.exp testcase
> currently does not exercise that, but the new test added by the
> patch below does.  That new test fails without the patch and passes
> with the patch.  No regressions on x86-64 GNU/Linux.  WDYT?
> 

AFAICT, the patch looks ok (just one nit below).

> +/* A static inlined function that is called by another static inlined
> +   function.  */
> +
> +static inline ATTR int
> +func_callee (int x)
> +{
> +  return x * 23;
> +}
> +
> +/* A static inlined function that calls another static inlined
> +   function.  The body of the function is a simple as possible so that
> +   both functions are inlined to the same PC address.  */
> +
> +static int

inline ATTR ?

> +func_caller (int x)
> +{
> +  return func_callee (x);
> +}
> +

Thanks,
- Tom

[pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Pedro Alves]

On 06/14/2018 02:22 PM, Tom de Vries wrote:
> On 06/12/2018 07:38 PM, Pedro Alves wrote:

>> Yes, sounds like it.  But the selftest.exp explicitly asks to stop
>> at "captured_main", not "captured_main_1", so I'm thinking that
>> it's gdb's behavior that might be wrong:
>>

> Agreed, that's a better solution.
> 
>> Note that both captured_main and captured_main_1 resolved to the
>> same address, 0x791339.  
> 
> Right. I played around a bit with this, and set breakpoints on
> captured_main and captured_main_1.
> 
> If I set a breakpoint on captured_main_1, we have captured_main unknown:
> ...
> Breakpoint 2, captured_main_1 (context=<optimized out>)
>     at /home/vries/gdb_versions/devel/src/gdb/main.c:492
> 492       lim_at_start = (char *) sbrk (0);
> (gdb) p captured_main
> No symbol "captured_main" in current context.
> (gdb) p captured_main_1
> $1 = {void (captured_main_args *)} 0x61b959
> <gdb_main(captured_main_args*)+25>
> ...
> 
> But If I set a breakpoint on captured_main instead, we have
> captured_main_1 unknown:
> ...
> Breakpoint 3, captured_main (data=<optimized out>)
>     at /home/vries/gdb_versions/devel/src/gdb/main.c:1147
> 1147      captured_main_1 (context);
> (gdb) p captured_main
> $2 = {void (void *)} 0x61b959 <gdb_main(captured_main_args*)+25>
> (gdb) p captured_main_1
> No symbol "captured_main_1" in current context.
> ...
> 
> And if I set a breakpoint on both, captured_main_1 seems to take
> precedence (independent of the order used to set the breakpoint):
> ...
> Breakpoint 1, captured_main_1 (context=<optimized out>)
>     at /home/vries/gdb_versions/devel/src/gdb/main.c:492
> 492       lim_at_start = (char *) sbrk (0);
> (gdb) p captured_main_1
> $1 = {void (captured_main_args *)} 0x61b959
> <gdb_main(captured_main_args*)+25>
> (gdb) p captured_main
> No symbol "captured_main" in current context.
> ...
> 
> I don't understand the underlying mechanisms well enough to decide
> whether this is a problem or not, but I thought I just mention it.

Can't pinpoint offhand where the problem is, but sounds like
something in the dwarf or elf symbol readers, maybe the breakpoint
you set first changes the order in which symbols are read and are
added to search hashes etc., or something like that.

It's most certainly unrelated to this change though.

> 
>> The gdb.base/inline-break.exp testcase
>> currently does not exercise that, but the new test added by the
>> patch below does.  That new test fails without the patch and passes
>> with the patch.  No regressions on x86-64 GNU/Linux.  WDYT?
>>
> 
> AFAICT, the patch looks ok (just one nit below).
> 
>> +/* A static inlined function that is called by another static inlined
>> +   function.  */
>> +
>> +static inline ATTR int
>> +func_callee (int x)
>> +{
>> +  return x * 23;
>> +}
>> +
>> +/* A static inlined function that calls another static inlined
>> +   function.  The body of the function is a simple as possible so that
>> +   both functions are inlined to the same PC address.  */
>> +
>> +static int
> 
> inline ATTR ?

Hmm, indeed.  If I do that however gcc (7.3) seemingly optimizes out
the functions more aggressively and we can't set a breakpoint anymore:

 (gdb) b func_inline_caller
 Function "func_inline_caller" not defined.
 Breakpoint 1 (func_inline_caller) pending.

A quick look at the debug info reveals that the debug info
does mention the functions, so this may be another gdb bug:

 <1><2c3>: Abbrev Number: 12 (DW_TAG_subprogram)
    <2c4>   DW_AT_name        : (indirect string, offset: 0x16f): func_inline_caller
    <2c8>   DW_AT_decl_file   : 1
    <2c9>   DW_AT_decl_line   : 197
    <2ca>   DW_AT_prototyped  : 1
    <2ca>   DW_AT_type        : <0x2a4>
    <2ce>   DW_AT_inline      : 3       (declared as inline and inlined)
    <2cf>   DW_AT_sibling     : <0x2dd>
...
 <1><2dd>: Abbrev Number: 12 (DW_TAG_subprogram)
    <2de>   DW_AT_name        : (indirect string, offset: 0x112): func_inline_callee
    <2e2>   DW_AT_decl_file   : 1
    <2e3>   DW_AT_decl_line   : 187
    <2e4>   DW_AT_prototyped  : 1
    <2e4>   DW_AT_type        : <0x2a4>
    <2e8>   DW_AT_inline      : 3       (declared as inline and inlined)
    <2e9>   DW_AT_sibling     : <0x2f7>

I haven't investigated that one.
In order to move forward with the frame skipping patch, I'm
adding a non-inline caller level in the testcase instead.

Below's what I've now merged.

From 4de1f9e76460db0f6b97762ff368e5b8f0da16b0 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Tue, 19 Jun 2018 16:30:13 +0100
Subject: [PATCH] Change inline frame breakpoint skipping logic (fix
 gdb.gdb/selftest.exp)

Currently, gdb.gdb/selftest.exp fails if you build GDB with
optimization (-O2, etc.).

The reason is that after setting a breakpoint in captured_main, we
stop at:
 ...
 Breakpoint 1, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
 ...
while selftest_setup expects a stop at captured_main.

Here, captured_main_1 has been inlined into captured_main, and
captured_main has been inlined into gdb_main:

 ...
 $ nm ./build/gdb/gdb | egrep ' [tT] .*captured_main|gdb_main' | c++filt
 000000000061b950 T gdb_main(captured_main_args*)
 ...

Indeed, the two inlined functions show up in the backtrace:

 ...
 (gdb) bt
 #0  captured_main_1 (context=<optimized out>) at main.c:492
 #1  captured_main (data=<optimized out>) at main.c:1147
 #2  gdb_main (args=args@entry=0x7fffffffdb80) at main.c:1173
 #3  0x000000000040fea5 in main (argc=<optimized out>, argv=<optimized out>)
     at gdb.c:32
 ...

We're now stopping at captured_main_1 because commit ddfe970e6bec
("Don't elide all inlined frames") makes GDB present a stop at the
innermost inlined frame if the program stopped by a user breakpoint.

Now, the selftest.exp testcase explicitly asks to stop at
"captured_main", not "captured_main_1", so I'm thinking that it's
GDB'S behavior that should be improved.  That is what this commit
does, by only showing a stop at an inline frame if the user breakpoint
was set in that frame's block.

Before this commit:

 (top-gdb) b captured_main
 Breakpoint 1 at 0x792f99: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb

 Breakpoint 1, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
 492       lim_at_start = (char *) sbrk (0);
 (top-gdb)

After this commit, we now instead get:

 (top-gdb) b captured_main
 Breakpoint 1 at 0x791339: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb

 Breakpoint 1, captured_main (data=<optimized out>) at src/gdb/main.c:1147
 1147      captured_main_1 (context);
 (top-gdb)

and:

 (top-gdb) b captured_main_1
 Breakpoint 2 at 0x791339: file src/gdb/main.c, line 492.
 (top-gdb) r
 Starting program: build/gdb/gdb
 Breakpoint 2, captured_main_1 (context=<optimized out>) at src/gdb/main.c:492
 492       lim_at_start = (char *) sbrk (0);
 (top-gdb)

Note that both captured_main and captured_main_1 resolved to the same
address, 0x791339.  That is necessary to trigger the issue in
question.  The gdb.base/inline-break.exp testcase currently does not
exercise that, but the new test added by this commit does.  That new
test fails without the GDB fix and passes with the fix.  No
regressions on x86-64 GNU/Linux.

While at it, the THIS_PC comparison in stopped_by_user_bp_inline_frame
is basically a nop, so just remove it -- if a software or hardware
breakpoint explains the stop, then it must be that it was installed at
the current PC.

gdb/ChangeLog:
2018-06-19  Pedro Alves  <palves@redhat.com>

	* inline-frame.c (stopped_by_user_bp_inline_frame): Replace PC
	parameter with a block parameter.  Compare location's block symbol
	with the frame's block instead of addresses.
	(skip_inline_frames): Pass the current block instead of the
	frame's address.  Break out as soon as we determine the frame
	should not be skipped.

gdb/testsuite/ChangeLog:
2018-06-19  Pedro Alves  <palves@redhat.com>

	* gdb.opt/inline-break.c (func_inline_callee, func_inline_caller)
	(func_extern_caller): New.
	(main): Call func_extern_caller.
	* gdb.opt/inline-break.exp: Add tests for inline frame skipping
	logic change.
---
 gdb/inline-frame.c                     | 23 +++++++++++------------
 gdb/testsuite/gdb.opt/inline-break.c   | 34 ++++++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.opt/inline-break.exp | 25 +++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index 1ac5835438d..3edd5b2b20b 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -286,11 +286,10 @@ block_starting_point_at (CORE_ADDR pc, const struct block *block)
 }
 
 /* Loop over the stop chain and determine if execution stopped in an
-   inlined frame because of a user breakpoint.  THIS_PC is the current
-   frame's PC.  */
+   inlined frame because of a user breakpoint set at FRAME_BLOCK.  */
 
 static bool
-stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
+stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 {
   for (bpstat s = stop_chain; s != NULL; s = s->next)
     {
@@ -301,9 +300,9 @@ stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
 	  bp_location *loc = s->bp_location_at;
 	  enum bp_loc_type t = loc->loc_type;
 
-	  if (loc->address == this_pc
-	      && (t == bp_loc_software_breakpoint
-		  || t == bp_loc_hardware_breakpoint))
+	  if ((t == bp_loc_software_breakpoint
+	       || t == bp_loc_hardware_breakpoint)
+	      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 	    return true;
 	}
     }
@@ -340,12 +339,12 @@ skip_inline_frames (ptid_t ptid, bpstat stop_chain)
 		{
 		  /* Do not skip the inlined frame if execution
 		     stopped in an inlined frame because of a user
-		     breakpoint.  */
-		  if (!stopped_by_user_bp_inline_frame (this_pc, stop_chain))
-		    {
-		      skip_count++;
-		      last_sym = BLOCK_FUNCTION (cur_block);
-		    }
+		     breakpoint for this inline function.  */
+		  if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
+		    break;
+
+		  skip_count++;
+		  last_sym = BLOCK_FUNCTION (cur_block);
 		}
 	      else
 		break;
diff --git a/gdb/testsuite/gdb.opt/inline-break.c b/gdb/testsuite/gdb.opt/inline-break.c
index 922102debb6..f64a81af939 100644
--- a/gdb/testsuite/gdb.opt/inline-break.c
+++ b/gdb/testsuite/gdb.opt/inline-break.c
@@ -176,6 +176,38 @@ not_inline_func3 (int x)
   return y + inline_func3 (x);
 }
 
+/* The following three functions serve to exercise GDB's inline frame
+   skipping logic when setting a user breakpoint on an inline function
+   by name.  */
+
+/* A static inlined function that is called by another static inlined
+   function.  */
+
+static inline ATTR int
+func_inline_callee (int x)
+{
+  return x * 23;
+}
+
+/* A static inlined function that calls another static inlined
+   function.  The body of the function is as simple as possible so
+   that both functions are inlined to the same PC address.  */
+
+static inline ATTR int
+func_inline_caller (int x)
+{
+  return func_inline_callee (x);
+}
+
+/* An extern not-inline function that calls a static inlined
+   function.  */
+
+int
+func_extern_caller (int x)
+{
+  return func_inline_caller (x);
+}
+
 /* Entry point.  */
 
 int
@@ -205,5 +237,7 @@ main (int argc, char *argv[])
 
   x = not_inline_func3 (-21);
 
+  func_extern_caller (1);
+
   return x;
 }
diff --git a/gdb/testsuite/gdb.opt/inline-break.exp b/gdb/testsuite/gdb.opt/inline-break.exp
index 008ff1ac33a..bae76254905 100644
--- a/gdb/testsuite/gdb.opt/inline-break.exp
+++ b/gdb/testsuite/gdb.opt/inline-break.exp
@@ -231,4 +231,29 @@ foreach_with_prefix cmd [list "break" "tbreak"] {
     }
 }
 
+# func_extern_caller calls func_inline_caller which calls
+# func_inline_callee.  The latter two are both inline functions.  Test
+# that setting a breakpoint on each of the functions reports a stop at
+# that function.  This exercises the inline frame skipping logic.  If
+# we set a breakpoint at function A, we want to present the stop at A,
+# even if A's entry code is an inlined call to another inline function
+# B.
+
+foreach_with_prefix func {
+    "func_extern_caller"
+    "func_inline_caller"
+    "func_inline_callee"
+} {
+    clean_restart $binfile
+
+    if {![runto main]} {
+	untested "could not run to main"
+	continue
+    }
+
+    gdb_breakpoint $func
+    gdb_test "continue" "Breakpoint .* $func .*at .*$srcfile.*" \
+	"breakpoint hit presents stop at breakpointed function"
+}
+
 unset -nocomplain results
-- 
2.14.3

Re: [pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Joel Brobecker]

Hello,

> gdb/ChangeLog:
> 2018-06-19  Pedro Alves  <palves@redhat.com>
>
> 	* inline-frame.c (stopped_by_user_bp_inline_frame): Replace PC
> 	parameter with a block parameter.  Compare location's block symbol
> 	with the frame's block instead of addresses.
> 	(skip_inline_frames): Pass the current block instead of the
> 	frame's address.  Break out as soon as we determine the frame
> 	should not be skipped.
>
> gdb/testsuite/ChangeLog:
> 2018-06-19  Pedro Alves  <palves@redhat.com>
>
> 	* gdb.opt/inline-break.c (func_inline_callee, func_inline_caller)
> 	(func_extern_caller): New.
> 	(main): Call func_extern_caller.
> 	* gdb.opt/inline-break.exp: Add tests for inline frame skipping
> 	logic change.

it looks like this patch is causing a crash with the following
example program:

    $ cat -n r.h
         1	/* r.h */
         2	int counter = 42;
         3
         4	inline void
         5	callee () {
         6	  counter = 0;  /* break here */
         7	}
    $ cat -n r.c
         1	/* r.c */
         2	#include "r.h"
         3
         4	int
         5	main ()
         6	{
         7	  callee ();
         8	}

I compiled it using the following commands:

    $ gcc -c -g -O2 r.c
    $ gcc -o r r.o

Then, trying to put a breakpoint on r.h:6 (inside "callee") causes
a SEGV for me:

    $ gdb -q r
    Reading symbols from r...done.
    (gdb) b r.h:6
    Breakpoint 1 at 0x4003c0: file r.h, line 6.
    (gdb) run
    Starting program: /[...]/r
    [1]    75618 segmentation fault  /[...]/gdb -q r

Prior to this commit, the behavior is the following for the "run"
command:

    (gdb) run
    Starting program: /[...]/r

    Breakpoint 1, callee () at r.h:6
    6	  counter = 0;  /* break here */

The problem occurs because we apparently assume that a bp_location's
symbols is not NULL:

    Program received signal SIGSEGV, Segmentation fault.
    0x00000000006f42bb in stopped_by_user_bp_inline_frame (
        stop_chain=<optimized out>, frame_block=<optimized out>)
        at /homes/brobecke/act/gdb/gdb-head/gdb/inline-frame.c:305
    305		      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
    (gdb) p loc->symbol
    $1 = (const symbol *) 0x0

I don't know yet whether that's a valid assumption or something
occurred earlier in the process. Any thoughts on this before I start
looking deeper?

I'm using a version of GCC 7.3.1 on x86_64-linux if anyone wants to
reproduce.

-- 
Joel

Re: [pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Pedro Alves]

On 06/25/2018 10:04 PM, Joel Brobecker wrote:
> Hello,
> 
>> gdb/ChangeLog:
>> 2018-06-19  Pedro Alves  <palves@redhat.com>
>>
>> 	* inline-frame.c (stopped_by_user_bp_inline_frame): Replace PC
>> 	parameter with a block parameter.  Compare location's block symbol
>> 	with the frame's block instead of addresses.
>> 	(skip_inline_frames): Pass the current block instead of the
>> 	frame's address.  Break out as soon as we determine the frame
>> 	should not be skipped.
>>
>> gdb/testsuite/ChangeLog:
>> 2018-06-19  Pedro Alves  <palves@redhat.com>
>>
>> 	* gdb.opt/inline-break.c (func_inline_callee, func_inline_caller)
>> 	(func_extern_caller): New.
>> 	(main): Call func_extern_caller.
>> 	* gdb.opt/inline-break.exp: Add tests for inline frame skipping
>> 	logic change.
> 
> it looks like this patch is causing a crash with the following
> example program:
> 
>     $ cat -n r.h
>          1	/* r.h */
>          2	int counter = 42;
>          3
>          4	inline void
>          5	callee () {
>          6	  counter = 0;  /* break here */
>          7	}
>     $ cat -n r.c
>          1	/* r.c */
>          2	#include "r.h"
>          3
>          4	int
>          5	main ()
>          6	{
>          7	  callee ();
>          8	}
> 
> I compiled it using the following commands:
> 
>     $ gcc -c -g -O2 r.c
>     $ gcc -o r r.o
> 
> Then, trying to put a breakpoint on r.h:6 (inside "callee") causes
> a SEGV for me:
> 
>     $ gdb -q r
>     Reading symbols from r...done.
>     (gdb) b r.h:6
>     Breakpoint 1 at 0x4003c0: file r.h, line 6.
>     (gdb) run
>     Starting program: /[...]/r
>     [1]    75618 segmentation fault  /[...]/gdb -q r
> 
> Prior to this commit, the behavior is the following for the "run"
> command:
> 
>     (gdb) run
>     Starting program: /[...]/r
> 
>     Breakpoint 1, callee () at r.h:6
>     6	  counter = 0;  /* break here */
> 
> The problem occurs because we apparently assume that a bp_location's
> symbols is not NULL:
> 
>     Program received signal SIGSEGV, Segmentation fault.
>     0x00000000006f42bb in stopped_by_user_bp_inline_frame (
>         stop_chain=<optimized out>, frame_block=<optimized out>)
>         at /homes/brobecke/act/gdb/gdb-head/gdb/inline-frame.c:305
>     305		      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
>     (gdb) p loc->symbol
>     $1 = (const symbol *) 0x0

Whoops.  I remember actually thinking about loc->symbol potentially
being null, but somehow convinced myself that SYMBOL_BLOCK_VALUE
would return null in that case...  :-P

> 
> I don't know yet whether that's a valid assumption or something
> occurred earlier in the process. Any thoughts on this before I start
> looking deeper?
> 
> I'm using a version of GCC 7.3.1 on x86_64-linux if anyone wants to
> reproduce.

If we just add a "loc->symbol != NULL" check, then we end up
presenting the stop at the caller of the inline function, where
the inline function was inlined, which is not what we want, since that's
not where the user set the breakpoint.

Recording the symbol in the location (it is copied from the sal
that linespec.c creates into the location by
add_location_to_breakpoint), like in the patch below, makes gdb present
the stop at  the "break here" line successfully.

I tried to come up with a more complicated testcase that included
more nested blocks inside the inlined function, to see if we would
need to record the inner inlined block in the sal instead of the
function's symbol (does that actually make sense for inlined functions?),
but all I came up with worked with this patch as is.  So maybe we
can defer thinking about that until we find a testcase?

From ac746927c3a8078098729dc3256010b2c1e617f8 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Tue, 26 Jun 2018 19:14:41 +0100
Subject: [PATCH] inline

---
 gdb/inline-frame.c | 1 +
 gdb/linespec.c     | 1 +
 2 files changed, 2 insertions(+)

diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index 896b0004e4a..3d07f8d0970 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -302,6 +302,7 @@ stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 
 	  if ((t == bp_loc_software_breakpoint
 	       || t == bp_loc_hardware_breakpoint)
+	      && loc->symbol != nullptr
 	      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 	    return true;
 	}
diff --git a/gdb/linespec.c b/gdb/linespec.c
index ae0200b8133..93e66c389f7 100644
--- a/gdb/linespec.c
+++ b/gdb/linespec.c
@@ -2196,6 +2196,7 @@ create_sals_line_offset (struct linespec_state *self,
 
 	    if (self->funfirstline)
 	      skip_prologue_sal (&intermediate_results[i]);
+	    intermediate_results[i].symbol = sym;
 	    add_sal_to_sals (self, &values, &intermediate_results[i],
 			     sym ? SYMBOL_NATURAL_NAME (sym) : NULL, 0);
 	  }
-- 
2.14.4

Thanks,
Pedro Alves

Re: [pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Joel Brobecker]

Hi Pedro,

> >     Program received signal SIGSEGV, Segmentation fault.
> >     0x00000000006f42bb in stopped_by_user_bp_inline_frame (
> >         stop_chain=<optimized out>, frame_block=<optimized out>)
> >         at /homes/brobecke/act/gdb/gdb-head/gdb/inline-frame.c:305
> >     305		      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
> >     (gdb) p loc->symbol
> >     $1 = (const symbol *) 0x0
> 
> Whoops.  I remember actually thinking about loc->symbol potentially
> being null, but somehow convinced myself that SYMBOL_BLOCK_VALUE
> would return null in that case...  :-P
> 
> > 
> > I don't know yet whether that's a valid assumption or something
> > occurred earlier in the process. Any thoughts on this before I start
> > looking deeper?
> > 
> > I'm using a version of GCC 7.3.1 on x86_64-linux if anyone wants to
> > reproduce.
> 
> If we just add a "loc->symbol != NULL" check, then we end up
> presenting the stop at the caller of the inline function, where
> the inline function was inlined, which is not what we want, since that's
> not where the user set the breakpoint.
> 
> Recording the symbol in the location (it is copied from the sal
> that linespec.c creates into the location by
> add_location_to_breakpoint), like in the patch below, makes gdb present
> the stop at  the "break here" line successfully.
> 
> I tried to come up with a more complicated testcase that included
> more nested blocks inside the inlined function, to see if we would
> need to record the inner inlined block in the sal instead of the
> function's symbol (does that actually make sense for inlined functions?),
> but all I came up with worked with this patch as is.  So maybe we
> can defer thinking about that until we find a testcase?

Just a quick message that the patch makes sense to me, and that
I was just able to run it through AdaCore's testsuite with succes.
Or, I should qualify that - there is one tiny change that I haven't
had time to analyze, but from the surface, it is exactly what you
explained about why you need the second hunk.

I haven't had a chance to run it through the official testsuite,
however, as I have to go ... I am so laaaaate!

I can do that tomorrow, or if you prefer to just finish the patch
up and push it, it'd be perfect. I think the patch is good.

Thanks again!

> 
> >From ac746927c3a8078098729dc3256010b2c1e617f8 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <palves@redhat.com>
> Date: Tue, 26 Jun 2018 19:14:41 +0100
> Subject: [PATCH] inline
> 
> ---
>  gdb/inline-frame.c | 1 +
>  gdb/linespec.c     | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
> index 896b0004e4a..3d07f8d0970 100644
> --- a/gdb/inline-frame.c
> +++ b/gdb/inline-frame.c
> @@ -302,6 +302,7 @@ stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
>  
>  	  if ((t == bp_loc_software_breakpoint
>  	       || t == bp_loc_hardware_breakpoint)
> +	      && loc->symbol != nullptr
>  	      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
>  	    return true;
>  	}
> diff --git a/gdb/linespec.c b/gdb/linespec.c
> index ae0200b8133..93e66c389f7 100644
> --- a/gdb/linespec.c
> +++ b/gdb/linespec.c
> @@ -2196,6 +2196,7 @@ create_sals_line_offset (struct linespec_state *self,
>  
>  	    if (self->funfirstline)
>  	      skip_prologue_sal (&intermediate_results[i]);
> +	    intermediate_results[i].symbol = sym;
>  	    add_sal_to_sals (self, &values, &intermediate_results[i],
>  			     sym ? SYMBOL_NATURAL_NAME (sym) : NULL, 0);
>  	  }
> -- 
> 2.14.4
> 
> Thanks,
> Pedro Alves

-- 
Joel

Re: [pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Pedro Alves]

Hi Joel,

On 06/26/2018 11:02 PM, Joel Brobecker wrote:

> Just a quick message that the patch makes sense to me, and that
> I was just able to run it through AdaCore's testsuite with succes.
> Or, I should qualify that - there is one tiny change that I haven't
> had time to analyze, but from the surface, it is exactly what you
> explained about why you need the second hunk.
> 
> I haven't had a chance to run it through the official testsuite,
> however, as I have to go ... I am so laaaaate!
> 
> I can do that tomorrow, or if you prefer to just finish the patch
> up and push it, it'd be perfect. I think the patch is good.
> 
> Thanks again!

FYI, I'm starting to look at this now.

Thanks,
Pedro Alves

Re: [pushed] Change inline frame breakpoint skipping logic (fix gdb.gdb/selftest.exp)

[Pedro Alves]

On 06/27/2018 05:28 PM, Pedro Alves wrote:
> Hi Joel,
> 
> On 06/26/2018 11:02 PM, Joel Brobecker wrote:
> 
>> Just a quick message that the patch makes sense to me, and that
>> I was just able to run it through AdaCore's testsuite with succes.
>> Or, I should qualify that - there is one tiny change that I haven't
>> had time to analyze, but from the surface, it is exactly what you
>> explained about why you need the second hunk.
>>
>> I haven't had a chance to run it through the official testsuite,
>> however, as I have to go ... I am so laaaaate!
>>
>> I can do that tomorrow, or if you prefer to just finish the patch
>> up and push it, it'd be perfect. I think the patch is good.
>>
>> Thanks again!
> 
> FYI, I'm starting to look at this now.

So while poking some more at this, noticed that setting a breakpoint
by address crashes in the same way, like "b *ADDRESS".  So I thought
that maybe it would be better to make stopped_by_user_bp_inline_frame
return true if the location has no symbol instead of returning
false like in the version I sent before.  That preserves the previous
behavior of showing the stop at the inline function if we miss
setting the sal's symbol somewhere.

However, playing with that made me notice something else
unrelated to my "Change inline frame breakpoint skipping"
patch:

  (gdb) b *0x40062f
  Breakpoint 2 at 0x40062f: file inline-break.c, line 32.
  (gdb) info breakpoints
  Num     Type           Disp Enb Address            What
  2       breakpoint     keep y   0x000000000040062f in main at inline-break.c:32
   (gdb) r
   ....
  Breakpoint 2, func1 (x=1) at inline-break.c:32
  32        return x * 23; /* break here */

Notice that above "info break" says "in main":

   in main at inline-break.c:32
      ^^^^

Since we say "inline-break.c:32" everywhere, and present the
stop at the inline function, I think that "info break" should say instead:

   in func1 at inline-break.c:32
      ^^^^^

Fixing that ends up going back to setting the symbol in the sal
again, but I decided to do that in a separate patch, and still
make "loc->symbol == nullptr" in stopped_by_user_bp_inline_frame return
true, unlike the previous version of the patch.

I'll be sending two patches in response to this email.

Thanks,
Pedro Alves

[PATCH 1/2] Fix running to breakpoint set in inline function by lineno/address

[Pedro Alves]

Commit 61b04dd04ac2 ("Change inline frame breakpoint skipping logic
(fix gdb.gdb/selftest.exp)") caused a GDB crash when you set a
breakpoint by line number in an inline function, and then run to the
breakpoint:

    $ gdb -q test Reading symbols from test...done.
    (gdb) b inline-break.c:32
    Breakpoint 1 at 0x40062f: file inline-break.c, line 32.
    (gdb) run
    Starting program: /[...]/test
    [1]    75618 segmentation fault  /[...]/gdb -q test

The problem occurs because we assume that a bp_location's symbol is
not NULL, which is not true when we set the breakpoint with a linespec
location:

    Program received signal SIGSEGV, Segmentation fault.
    0x00000000006f42bb in stopped_by_user_bp_inline_frame (
        stop_chain=<optimized out>, frame_block=<optimized out>)
        at gdb/inline-frame.c:305
    305		      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
    (gdb) p loc->symbol
    $1 = (const symbol *) 0x0

The same thing happens if you run to a breakpoint set in an inline
function by address:

  (gdb) b *0x40062f
  Breakpoint 3 at 0x40062f: file inline-break.c, line 32.

To fix this, add a null pointer check, to avoid the crash, and make it
so that if there's not symbol for the location, then we present the
stop at the inline function.  This preserves the previous behavior
when e.g., setting a breakpoint by address, with "b *ADDRESS".

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* inline-frame.c (stopped_by_user_bp_inline_frame): Return
	true if the the location has no symbol.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* gdb.opt/inline-break.c (func1): Add "break here" marker.
	* gdb.opt/inline-break.exp: Test setting breakpoints by line
	number and address and running to them.
---
 gdb/inline-frame.c                     | 16 +++++++++----
 gdb/testsuite/gdb.opt/inline-break.c   |  2 +-
 gdb/testsuite/gdb.opt/inline-break.exp | 42 ++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index 896b0004e4a..c6caf9d0c6e 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -300,10 +300,18 @@ stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 	  bp_location *loc = s->bp_location_at;
 	  enum bp_loc_type t = loc->loc_type;
 
-	  if ((t == bp_loc_software_breakpoint
-	       || t == bp_loc_hardware_breakpoint)
-	      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
-	    return true;
+	  if (t == bp_loc_software_breakpoint
+	      || t == bp_loc_hardware_breakpoint)
+	    {
+	      /* If the location has a function symbol, check whether
+		 the frame was for that inlined function.  If it has
+		 no function symbol, then assume it is.  I.e., default
+		 to presenting the stop at the innermost inline
+		 function.  */
+	      if (loc->symbol == nullptr
+		  || frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
+		return true;
+	    }
 	}
     }
 
diff --git a/gdb/testsuite/gdb.opt/inline-break.c b/gdb/testsuite/gdb.opt/inline-break.c
index f64a81af939..d4779299fa2 100644
--- a/gdb/testsuite/gdb.opt/inline-break.c
+++ b/gdb/testsuite/gdb.opt/inline-break.c
@@ -29,7 +29,7 @@
 static inline ATTR int
 func1 (int x)
 {
-  return x * 23;
+  return x * 23; /* break here */
 }
 
 /* A non-static inlined function that is called once.  */
diff --git a/gdb/testsuite/gdb.opt/inline-break.exp b/gdb/testsuite/gdb.opt/inline-break.exp
index bae76254905..68b7b89ef31 100644
--- a/gdb/testsuite/gdb.opt/inline-break.exp
+++ b/gdb/testsuite/gdb.opt/inline-break.exp
@@ -256,4 +256,46 @@ foreach_with_prefix func {
 	"breakpoint hit presents stop at breakpointed function"
 }
 
+# Test setting a breakpoint in an inline function by line number and
+# by address, and that GDB presents the stop there.
+
+set line [gdb_get_line_number "break here"]
+
+with_test_prefix "line number" {
+    clean_restart $binfile
+
+    if {![runto main]} {
+	untested "could not run to main"
+	continue
+    }
+
+    # Set the breakpoint by line number, and check that GDB reports
+    # the breakpoint location being the inline function.
+    gdb_breakpoint "$srcfile:$line"
+    gdb_test "continue" "Breakpoint .*, func1 \\(x=1\\) at .*$srcfile:$line.*break here.*" \
+	"breakpoint hit presents stop at inlined function"
+
+    # Save the PC for the following by-address test.
+    set address [get_hexadecimal_valueof "\$pc" "0"]
+}
+
+# Test setting a breakpoint in an inline function by address, and that
+# GDB presents the stop there.
+
+with_test_prefix "address" {
+
+    clean_restart $binfile
+
+    if {![runto main]} {
+	untested "could not run to main"
+	continue
+    }
+
+    # Set the breakpoint by address, and check that GDB reports the
+    # breakpoint location being the inline function.
+    gdb_test "break *$address" ".*Breakpoint .* at $address: file .*$srcfile, line $line."
+    gdb_test "continue" "Breakpoint .*, func1 \\(x=1\\) at .*$srcfile:$line.*break here.*" \
+	"breakpoint hit presents stop at inlined function"
+}
+
 unset -nocomplain results
-- 
2.14.4

[PATCH 2/2] "break LINENO/*ADDRESS", inline functions and "info break" output

[Pedro Alves]

While experimenting with the previous patch, I noticed this inconsistency
in GDB's output:

  (gdb) b 32
  Breakpoint 1 at 0x40062f: file inline-break.c, line 32.                  (1)
  (gdb) r
  ....
  Breakpoint 1, func1 (x=1) at inline-break.c:32                           (2)
  32        return x * 23; /* break here */
  (gdb) info breakpoints
  Num     Type           Disp Enb Address    What
  1       breakpoint     keep y   0x40062f   in main at inline-break.c:32  (3)
	  breakpoint already hit 1 time
  (gdb)

Notice that when the breakpoint as set, GDB showed "inline-break.c,
line 32" (1), the same line number that was specified in the command.

When we run to the breakpoint, we present the stop at the same line
number, and correctly show "func1" as the function name (2).

But in "info break" output (3), notice that we say "in main", not "in
func1".

The same thing happens if you set a breakpoint by address.  I.e.:

  (gdb) b *0x40062f
  Breakpoint 2 at 0x40062f: file inline-break.c, line 32.
  (gdb) info breakpoints
  Num     Type           Disp Enb Address            What
  2       breakpoint     keep y   0x000000000040062f in main at inline-break.c:32
   (gdb) r
   ....
  Breakpoint 2, func1 (x=1) at inline-break.c:32
  32        return x * 23; /* break here */

The problem is that the breakpoints were set at an inline function,
but when we set such a breakpoint by line number or address, we don't
record the functions symbol in the sal, and as consequence the
breakpoint location does not have an associated symbol either.

Then, in print_breakpoint_location, if the location does not have a
symbol, we call find_pc_sect_function to find one, and this is what
finds "main", because find_pc_sect_function uses
block_linkage_function:

  /* Return the symbol for the function which contains a specified
     lexical block, described by a struct block BL.  The return value
     will not be an inlined function; the containing function will be
     returned instead.  */

  struct symbol *
  block_linkage_function (const struct block *bl)

To fix this, this commit adds an alternative to find_pc_sect_function
that uses block_containing_function instead:

  /* Return the symbol for the function which contains a specified
     block, described by a struct block BL.  The return value will be
     the closest enclosing function, which might be an inline
     function.  */

  struct symbol *
  block_containing_function (const struct block *bl)

(It seems odd to me that block_linkage_function says "the CONTAINING
function will be returned", and then block_containing_function says it
returns "the closest enclosing function".  Something seems reversed
here.  Still, I've kept the same nomenclature and copied the comments,
so that at least there's consistency.  Maybe we should fix that up
somehow.)

Then I wondered, why make print_breakpoint_location look up the symbol
every time it is called, instead of just always storing the symbol
when the location is created, since the location already stores the
symbol in some cases.  So to find which cases might be missing setting
the symbol in the sal which is used to create the breakpoint location,
I added an assertion to print_breakpoint_location, and ran the
testsuite.  That caught a few places, unsurprisingly:

 - setting a breakpoint by line number
 - setting a breapoint by address
 - ifunc resolving

Those are all fixed by this commit.  I decided not to add the
assertion to block_linkage_function and leave the existing "if (sym)"
check in place, because it's plausible that we have symtabs with line
info but no symbols.  I.e., that would not be a GDB bug, but
a peculiarity of debug info input.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* blockframe.c (find_pc_sect_containing_function): New function.
	* breakpoint.c (print_breakpoint_location): Don't call
	find_pc_sect_function.
	* linespec.c (create_sals_line_offset): Record the location's
	symbol in the sal.
	* linespec.c (convert_address_location_to_sals): Fill in sal's
	symbol with find_pc_sect_containing_function.
	* symtab.c (find_function_start_sal): Rename to ...
	(find_function_start_sal_1): ... this.
	(find_function_start_sal): Reimplement as wrapper around
	find_function_start_sal_1, and use
	find_pc_sect_containing_function to fill in the sal's symbol.
	(find_function_start_sal(symbol*, bool)): Adjust.
	* symtab.h (find_pc_function, find_pc_sect_function): Adjust
	comments.
	(find_pc_sect_containing_function): Declare.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <palves@redhat.com>

	* gdb.opt/inline-break.exp (line number, address): Add "info
	break" tests.
---
 gdb/blockframe.c                       | 13 +++++++++++++
 gdb/breakpoint.c                       |  3 ---
 gdb/linespec.c                         |  2 ++
 gdb/symtab.c                           | 32 +++++++++++++++++++++++++-------
 gdb/symtab.h                           | 15 +++++++++++++--
 gdb/testsuite/gdb.opt/inline-break.exp |  6 ++++++
 6 files changed, 59 insertions(+), 12 deletions(-)

diff --git a/gdb/blockframe.c b/gdb/blockframe.c
index b3c9aa3bd73..6a018ccaefe 100644
--- a/gdb/blockframe.c
+++ b/gdb/blockframe.c
@@ -152,6 +152,19 @@ find_pc_function (CORE_ADDR pc)
   return find_pc_sect_function (pc, find_pc_mapped_section (pc));
 }
 
+/* See symtab.h.  */
+
+struct symbol *
+find_pc_sect_containing_function (CORE_ADDR pc, struct obj_section *section)
+{
+  const block *bl = block_for_pc_sect (pc, section);
+
+  if (bl == nullptr)
+    return nullptr;
+
+  return block_containing_function (bl);
+}
+
 /* These variables are used to cache the most recent result
    of find_pc_partial_function.  */
 
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 80df193a013..82dec7d418f 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -5867,9 +5867,6 @@ print_breakpoint_location (struct breakpoint *b,
     {
       const struct symbol *sym = loc->symbol;
 
-      if (sym == NULL)
-	sym = find_pc_sect_function (loc->address, loc->section);
-
       if (sym)
 	{
 	  uiout->text ("in ");
diff --git a/gdb/linespec.c b/gdb/linespec.c
index ae0200b8133..2a4189278ef 100644
--- a/gdb/linespec.c
+++ b/gdb/linespec.c
@@ -2196,6 +2196,7 @@ create_sals_line_offset (struct linespec_state *self,
 
 	    if (self->funfirstline)
 	      skip_prologue_sal (&intermediate_results[i]);
+	    intermediate_results[i].symbol = sym;
 	    add_sal_to_sals (self, &values, &intermediate_results[i],
 			     sym ? SYMBOL_NATURAL_NAME (sym) : NULL, 0);
 	  }
@@ -2224,6 +2225,7 @@ convert_address_location_to_sals (struct linespec_state *self,
   sal.pc = address;
   sal.section = find_pc_overlay (address);
   sal.explicit_pc = 1;
+  sal.symbol = find_pc_sect_containing_function (sal.pc, sal.section);
 
   std::vector<symtab_and_line> sals;
   add_sal_to_sals (self, &sals, &sal, core_addr_to_string (address), 1);
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 3e594e76c92..d8a7a16e073 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -3575,11 +3575,12 @@ find_pc_line_pc_range (CORE_ADDR pc, CORE_ADDR *startptr, CORE_ADDR *endptr)
   return sal.symtab != 0;
 }
 
-/* See symtab.h.  */
+/* Helper for find_function_start_sal.  Does most of the work, except
+   setting the sal's symbol.  */
 
-symtab_and_line
-find_function_start_sal (CORE_ADDR func_addr, obj_section *section,
-			 bool funfirstline)
+static symtab_and_line
+find_function_start_sal_1 (CORE_ADDR func_addr, obj_section *section,
+			   bool funfirstline)
 {
   symtab_and_line sal = find_pc_sect_line (func_addr, section, 0);
 
@@ -3615,14 +3616,31 @@ find_function_start_sal (CORE_ADDR func_addr, obj_section *section,
 
 /* See symtab.h.  */
 
+symtab_and_line
+find_function_start_sal (CORE_ADDR func_addr, obj_section *section,
+			 bool funfirstline)
+{
+  symtab_and_line sal
+    = find_function_start_sal_1 (func_addr, section, funfirstline);
+
+  /* find_function_start_sal_1 does a linetable search, so it finds
+     the symtab and linenumber, but not a symbol.  Fill in the
+     function symbol too.  */
+  sal.symbol = find_pc_sect_containing_function (sal.pc, sal.section);
+
+  return sal;
+}
+
+/* See symtab.h.  */
+
 symtab_and_line
 find_function_start_sal (symbol *sym, bool funfirstline)
 {
   fixup_symbol_section (sym, NULL);
   symtab_and_line sal
-    = find_function_start_sal (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)),
-			       SYMBOL_OBJ_SECTION (symbol_objfile (sym), sym),
-			       funfirstline);
+    = find_function_start_sal_1 (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)),
+				 SYMBOL_OBJ_SECTION (symbol_objfile (sym), sym),
+				 funfirstline);
   sal.symbol = sym;
   return sal;
 }
diff --git a/gdb/symtab.h b/gdb/symtab.h
index 84fc8976582..0b155d06592 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -1670,14 +1670,25 @@ extern struct type *lookup_enum (const char *, const struct block *);
 
 /* from blockframe.c: */
 
-/* lookup the function symbol corresponding to the address.  */
+/* lookup the function symbol corresponding to the address.  The
+   return value will not be an inlined function; the containing
+   function will be returned instead.  */
 
 extern struct symbol *find_pc_function (CORE_ADDR);
 
-/* lookup the function corresponding to the address and section.  */
+/* lookup the function corresponding to the address and section.  The
+   return value will not be an inlined function; the containing
+   function will be returned instead.  */
 
 extern struct symbol *find_pc_sect_function (CORE_ADDR, struct obj_section *);
 
+/* lookup the function symbol corresponding to the address and
+   section.  The return value will be the closest enclosing function,
+   which might be an inline function.  */
+
+extern struct symbol *find_pc_sect_containing_function
+  (CORE_ADDR pc, struct obj_section *section);
+
 /* Find the symbol at the given address.  Returns NULL if no symbol
    found.  Only exact matches for ADDRESS are considered.  */
 
diff --git a/gdb/testsuite/gdb.opt/inline-break.exp b/gdb/testsuite/gdb.opt/inline-break.exp
index 68b7b89ef31..183a1b927c6 100644
--- a/gdb/testsuite/gdb.opt/inline-break.exp
+++ b/gdb/testsuite/gdb.opt/inline-break.exp
@@ -272,6 +272,9 @@ with_test_prefix "line number" {
     # Set the breakpoint by line number, and check that GDB reports
     # the breakpoint location being the inline function.
     gdb_breakpoint "$srcfile:$line"
+
+    gdb_test "info break \$bpnum" "in func1 at .*$srcfile:$line"
+
     gdb_test "continue" "Breakpoint .*, func1 \\(x=1\\) at .*$srcfile:$line.*break here.*" \
 	"breakpoint hit presents stop at inlined function"
 
@@ -294,6 +297,9 @@ with_test_prefix "address" {
     # Set the breakpoint by address, and check that GDB reports the
     # breakpoint location being the inline function.
     gdb_test "break *$address" ".*Breakpoint .* at $address: file .*$srcfile, line $line."
+
+    gdb_test "info break \$bpnum" "in func1 at .*$srcfile:$line"
+
     gdb_test "continue" "Breakpoint .*, func1 \\(x=1\\) at .*$srcfile:$line.*break here.*" \
 	"breakpoint hit presents stop at inlined function"
 }
-- 
2.14.4

Re: [PATCH 1/2] Fix running to breakpoint set in inline function by lineno/address

[Joel Brobecker]

> Commit 61b04dd04ac2 ("Change inline frame breakpoint skipping logic
> (fix gdb.gdb/selftest.exp)") caused a GDB crash when you set a
> breakpoint by line number in an inline function, and then run to the
> breakpoint:
> 
>     $ gdb -q test Reading symbols from test...done.
>     (gdb) b inline-break.c:32
>     Breakpoint 1 at 0x40062f: file inline-break.c, line 32.
>     (gdb) run
>     Starting program: /[...]/test
>     [1]    75618 segmentation fault  /[...]/gdb -q test
> 
> The problem occurs because we assume that a bp_location's symbol is
> not NULL, which is not true when we set the breakpoint with a linespec
> location:
> 
>     Program received signal SIGSEGV, Segmentation fault.
>     0x00000000006f42bb in stopped_by_user_bp_inline_frame (
>         stop_chain=<optimized out>, frame_block=<optimized out>)
>         at gdb/inline-frame.c:305
>     305		      && frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
>     (gdb) p loc->symbol
>     $1 = (const symbol *) 0x0
> 
> The same thing happens if you run to a breakpoint set in an inline
> function by address:
> 
>   (gdb) b *0x40062f
>   Breakpoint 3 at 0x40062f: file inline-break.c, line 32.
> 
> To fix this, add a null pointer check, to avoid the crash, and make it
> so that if there's not symbol for the location, then we present the
> stop at the inline function.  This preserves the previous behavior
> when e.g., setting a breakpoint by address, with "b *ADDRESS".
> 
> gdb/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
> 
> 	* inline-frame.c (stopped_by_user_bp_inline_frame): Return
> 	true if the the location has no symbol.
> 
> gdb/testsuite/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
> 
> 	* gdb.opt/inline-break.c (func1): Add "break here" marker.
> 	* gdb.opt/inline-break.exp: Test setting breakpoints by line
> 	number and address and running to them.

Thanks, Pedro. I had a look, and FWIW, the patch looks good to me.

-- 
Joel

Re: [PATCH 2/2] "break LINENO/*ADDRESS", inline functions and "info break" output

[Joel Brobecker]

Hi Pedro,

> While experimenting with the previous patch, I noticed this inconsistency
> in GDB's output:
[...]
> When we run to the breakpoint, we present the stop at the same line
> number, and correctly show "func1" as the function name (2).
> 
> But in "info break" output (3), notice that we say "in main", not "in
> func1".

> (It seems odd to me that block_linkage_function says "the CONTAINING
> function will be returned", and then block_containing_function says it
> returns "the closest enclosing function".  Something seems reversed
> here.  Still, I've kept the same nomenclature and copied the comments,
> so that at least there's consistency.  Maybe we should fix that up
> somehow.)

That seems opposite to me as well...

> Then I wondered, why make print_breakpoint_location look up the symbol
> every time it is called, instead of just always storing the symbol
> when the location is created, since the location already stores the
> symbol in some cases.

Agreed.

> So to find which cases might be missing setting
> the symbol in the sal which is used to create the breakpoint location,
> I added an assertion to print_breakpoint_location, and ran the
> testsuite.  That caught a few places, unsurprisingly:
> 
>  - setting a breakpoint by line number
>  - setting a breapoint by address
>  - ifunc resolving
> 
> Those are all fixed by this commit.

Nice approach!

> I decided not to add the
> assertion to block_linkage_function and leave the existing "if (sym)"
> check in place, because it's plausible that we have symtabs with line
> info but no symbols.  I.e., that would not be a GDB bug, but
> a peculiarity of debug info input.

Agreed as well.

> gdb/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
> 
> 	* blockframe.c (find_pc_sect_containing_function): New function.
> 	* breakpoint.c (print_breakpoint_location): Don't call
> 	find_pc_sect_function.
> 	* linespec.c (create_sals_line_offset): Record the location's
> 	symbol in the sal.
> 	* linespec.c (convert_address_location_to_sals): Fill in sal's
> 	symbol with find_pc_sect_containing_function.
> 	* symtab.c (find_function_start_sal): Rename to ...
> 	(find_function_start_sal_1): ... this.
> 	(find_function_start_sal): Reimplement as wrapper around
> 	find_function_start_sal_1, and use
> 	find_pc_sect_containing_function to fill in the sal's symbol.
> 	(find_function_start_sal(symbol*, bool)): Adjust.
> 	* symtab.h (find_pc_function, find_pc_sect_function): Adjust
> 	comments.
> 	(find_pc_sect_containing_function): Declare.

I know it might be considered a small and trivial part, but I really
appreciate the attention to the function's comment description.

> 
> gdb/testsuite/ChangeLog:
> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
> 
> 	* gdb.opt/inline-break.exp (line number, address): Add "info
> 	break" tests.

I went through the patch and it looks good.

Thanks again!
-- 
Joel

Re: [PATCH 2/2] "break LINENO/*ADDRESS", inline functions and "info break" output

[Pedro Alves]

On 06/28/2018 06:42 PM, Joel Brobecker wrote:

>> gdb/testsuite/ChangeLog:
>> yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
>>
>> 	* gdb.opt/inline-break.exp (line number, address): Add "info
>> 	break" tests.
> 
> I went through the patch and it looks good.

Great, thanks.  I pushed in both patches now.

Thanks,
Pedro Alves